'''
Access and control MicroPython internals

[View Doc](https://docs.micropython.org/en/latest/library/micropython.html)
'''
import typing


# Functions
def const(expr: int):
	'''
	Used to declare that the expression is a constant so that the compiler can
	optimise it.

	The use of this function should be as follows::

	    from micropython import const

	    CONST_X = const(123)
	    CONST_Y = const(2 * CONST_X + 1)

	Constants declared this way are still accessible as global variables from
	outside the module they are declared in.

	On the other hand, if a constant begins with an underscore then it is hidden,
	it is not available as a global variable, and does not take up any memory
	during execution.

	This const function is recognised directly by the MicroPython parser and is
	provided as part of the micropython module mainly so that scripts can be
	written which run under both CPython and MicroPython, by following the above
	pattern.
	'''

@typing.overload
def opt_level() -> int:
	'''It returns the current optimisation level.'''

@typing.overload
def opt_level(level: int = 0):
	'''
	This function sets the optimisation level for subsequent compilation of
	scripts, and returns `None`.

	The optimisation level controls the following compilation features:

	- Assertions: at level 0 assertion statements are enabled and compiled into
	the bytecode; at levels 1 and higher assertions are not compiled.
	- Built-in `__debug__` variable: at level 0 this variable expands to `True`; at
	levels 1 and higher it expands to `False`.
	- Source-code line numbers: at levels 0, 1 and 2 source-code line number are
	stored along with the bytecode so that exceptions can report the line number
	they occurred at; at levels 3 and higher line numbers are not stored.

	The default optimisation level is usually level 0.
	'''

def alloc_emergency_exception_buf(size: int):
	'''
	Allocate size bytes of RAM for the emergency exception buffer (a good size
	is around 100 bytes).

	The buffer is used to create exceptions in cases when normal RAM allocation
	would fail (eg within an interrupt handler) and therefore give useful
	traceback information in these situations.

	A good way to use this function is to put it at the start of your main script
	(eg `boot.py` or `main.py`) and then the emergency exception buffer will be active
	for all the code following it.
	'''

@typing.overload
def mem_info():
	'''
	Print information about currently used memory.

	The information that is printed is implementation dependent, but currently
	includes the amount of stack and heap used.
	'''

@typing.overload
def mem_info(verbose: typing.Any):
	'''
	The given then extra information is printed.

	The information that is printed is implementation dependent, it prints out
	the entire heap indicating which blocks are used and which are free.
	'''

@typing.overload
def qstr_info():
	'''
	Print information about currently interned strings.

	The information that is printed is implementation dependent, but currently
	includes the number of interned strings and the amount of RAM they use.
	'''

@typing.overload
def qstr_info(verbose: typing.Any):
	'''
	Print extra information about currently interned strings.

	The information that is printed is implementation dependent, it prints out
	the names of all RAM-interned strings.
	'''

def stack_use() -> int:
	'''
	Return an integer representing the current amount of stack that is being used.

	The absolute value of this is not particularly useful, rather it should be
	used to compute differences in stack usage at different points.
	'''

def heap_lock():
	'''
	Lock the heap.

	When locked no memory allocation can occur and a `MemoryError` will be raised
	if any heap allocation is attempted.

	This functions can be nested, ie `heap_lock()` can be called multiple times
	in a row and the lock-depth will increase, and then `heap_unlock()` must be
	called the same number of times to make the heap available again.
	'''

def heap_unlock() -> int:
	'''
	Unlock the heap.

	`heap_unlock()` return the current lock depth (after unlocking for the former)
	as a non-negative integer, with 0 meaning the heap is not locked.

	If the REPL becomes active with the heap locked then it will be forcefully
	unlocked.
	'''

def heap_locked() -> bool:
	'''
	Returns a `True` value if the heap is currently locked.

	If the REPL becomes active with the heap locked then it will be forcefully
	unlocked.

	Note:

		`heap_locked()` is not enabled on most ports by default, requires
		`MICROPY_PY_MICROPYTHON_HEAP_LOCKED`.
	'''

def kbd_intr(chr: int = 3):
	'''
	Set the character that will raise a `KeyboardInterrupt` exception.

	By default this is set to 3 during script execution, corresponding to Ctrl-C.

	Passing -1 to this function will disable capture of Ctrl-C, and passing 3
	will restore it.

	This function can be used to prevent the capturing of Ctrl-C on the incoming
	stream of characters that is usually used for the REPL, in case that stream
	is used for other purposes.
	'''

def schedule(func: function, arg):
	'''
	Schedule the function `func` to be executed "very soon".

	The function is passed the value `arg` as its single argument.

	"Very soon" means that the MicroPython runtime will do its best to execute
	the function at the earliest possible time, given that it is also trying to
	be efficient, and that the following conditions hold:

	- A scheduled function will never preempt another scheduled function.

	- Scheduled functions are always executed "between opcodes" which means that
	all fundamental Python operations (such as appending to a list) are guaranteed
	to be atomic.

	- A given port may define "critical regions" within which scheduled functions
	will never be executed.

		Functions may be scheduled within a critical region but they will not be
		executed until that region is exited.

		An example of a critical region is a preempting interrupt handler (an IRQ).

	A use for this function is to schedule a callback from a preempting IRQ.

	Such an IRQ puts restrictions on the code that runs in the IRQ (for example
	the heap may be locked) and scheduling a function to call later will lift
	those restrictions.

	Note:

		If `schedule()` is called from a preempting IRQ, when memory allocation
		is not allowed and the callback to be passed to `schedule()` is a bound
		method, passing this directly will fail.

		This is because creating a reference to a bound method causes memory
		allocation.

		A solution is to create a reference to the method in the class constructor
		and to pass that reference to `schedule()`.

		This is discussed in detail here reference documentation under "Creation
		of Python objects".

	There is a finite queue to hold the scheduled functions and `schedule()`
	will raise a `RuntimeError` if the queue is full.
	'''
